Taking lens device

ABSTRACT

A optical device has a zoom lens system that is comprised of a plurality of lens units and that achieves zooming by varying unit-to-unit distances and an image sensor that converts an optical image formed by the zoom lens system into an electrical signal. The zoom lens system is comprised of, from the object side, a first lens unit having a negative optical power, a second lens unit having a negative optical power, a third lens unit having a positive optical power, and a fourth lens unit having a positive optical power. The zoom lens system achieves zooming by varying the distances between the first to fourth lens units.

This application is based on Japanese Patent Applications Nos.2000-95247 and 2000-368343, filed on Mar. 29, 2000 and Dec. 4, 2000,respectively, the contents of which are hereby incorporated byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an optical device, or a taking lensdevice. More specifically, the present invention relates to a takinglens device that optically takes in an image of a subject through anoptical system and that then outputs the image as an electrical signal,for example, a taking lens device that is used as a main component of adigital still camera, a digital video camera, or a camera that isincorporated in or externally fitted to a device such as a digital videounit, a personal computer, a mobile computer, a portable telephone, or apersonal digital assistant (PDA). The present invention relatesparticularly to a taking lens device which is provided with a compact,high-zoom-ratio zoom lens system.

2. Description of Prior Art

In recent years, as personal computers and other data processing deviceshave become more and more popular, digital still cameras, digital videocameras, and the like (hereinafter collectively referred to as digitalcameras) have been coming into increasingly wide use. Personal users areusing these digital cameras as handy devices that permit easyacquisition of image data to be fed to digital devices. As image datainput devices, digital cameras are expected to continue gainingpopularity.

In general, the image quality of a digital camera depends on the numberof pixels in the solid-state image sensor, such as a CCD (charge-coupleddevice), which is incorporated therein. Nowadays, many digital cameraswhich are designed for general consumers, boast of high resolution ofover a million pixels, and are thus approaching silver-halide filmcameras in image quality. On the other hand, even in digital camerasdesigned for general consumers, zoom capability (especially optical zoomcapability with minimal image degradation) is desired, and therefore, inrecent years, there has been an increasing demand for zoom lenses fordigital cameras that offer both a high zoom ratio and high imagequality.

However, conventional zoom lenses for digital cameras that offer highimage quality of over a million pixels are usually built as relativelylarge lens systems. One way to avoid this inconvenience is to use, aszoom lenses for digital cameras, zoom lenses which were originallydesigned for lens-shutter cameras in which remarkable miniaturizationand zoom ratio enhancement have been achieved in recent years. However,if a zoom lens designed for a lens-shutter camera is used unchanged in adigital camera, it is not possible to make good use of thelight-condensing ability of the microlenses disposed on the frontsurface of the solid-state image sensor. This causes severe unevennessin brightness between a central portion and a peripheral portion of thecaptured image. The reason is that in a lens-shutter camera, the exitpupil of the taking lens system is located near the image plane, andtherefore off-axial rays exiting from the taking lens system strike theimage plane from oblique directions. This can be avoided by locating theexit pupil away from the image plane, but not without making the takinglens system larger.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an optical, or a takinglens device, which is provided with a novel zoom lens system that,despite being compact, offers both a high zoom ratio and high imagequality.

To achieve this object, according to one aspect of the presentinvention, an optical, or taking lens device is provided with: a zoomlens system that is comprised of a plurality of lens units whichachieves zooming by varying the unit-to-unit distances; and an imagesensor that converts an optical image formed by the zoom lens systeminto an electrical signal. The zoom lens system comprises at least, fromthe object side thereof to an image side thereof, a first lens unithaving a negative optical power, a second lens unit having a negativeoptical power, a third lens unit having a positive optical power, and afourth lens unit having a positive optical power. The zoom lens systemachieves zooming by varying the distances between the first to fourthlens units.

According to another aspect of the present invention, an optical, ortaking lens device is provided with: a zoom lens system that iscomprised of a plurality of lens units which achieves zooming by varyingthe unit-to-unit distances; and an image sensor that converts an opticalimage formed by the zoom lens system into an electrical signal. The zoomlens system is comprised of, at least from the object side, a first lensunit having a negative optical power, a second lens unit having anegative optical power, and a third lens unit having a positive opticalpower. The first lens unit comprises a single lens element.

BRIEF DESCRIPTION OF THE DRAWINGS

This and other objects and features of the present invention will becomeclear from the following description, taken in conjunction with thepreferred embodiments with reference to the accompanying drawings inwhich:

FIG. 1 is a lens arrangement diagram of a first embodiment (Example 1)of the invention;

FIG. 2 is a lens arrangement diagram of a second embodiment (Example 2)of the invention;

FIG. 3 is a lens arrangement diagram of a third embodiment (Example 3)of the invention;

FIG. 4 is a lens arrangement diagram of a fourth embodiment (Example 4)of the invention,

FIG. 5 is a lens arrangement diagram of a fifth embodiment (Example 5)of the invention;

FIG. 6 is a lens arrangement diagram of a sixth embodiment (Example 6)of the invention;

FIG. 7 is a lens arrangement diagram of a seventh embodiment (Example 7)of the invention;

FIG. 8 is a lens arrangement diagram of an eighth embodiment (Example 8)of the invention;

FIG. 9 is a lens arrangement diagram of a ninth embodiment (Example 9)of the invention;

FIGS. 10A to 10I are aberration diagrams of Example 1;

FIGS. 11A to 11I are aberration diagrams of Example 2;

FIGS. 12A to 12I are aberration diagrams of Example 3;

FIGS. 13A to 13I are aberration diagrams of Example 4;

FIGS. 14A to 14I are aberration diagrams of Example 5;

FIGS. 15A to 15I are aberration diagrams of Example 6;

FIGS. 16A to 16I are aberration diagrams of Example 7;

FIGS. 17A to 17I are aberration diagrams of Example 8;

FIGS. 18A to 18I are aberration diagrams of Example 9;

FIG. 19 is a diagram schematically illustrating the outline of theoptical construction of a taking lens device embodying the invention;and

FIG. 20 is a diagram schematically illustrating the outline of aconstruction of an embodiment of the invention that could be used in adigital camera.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, optical or taking lens devices embodying the presentinvention will be described with reference to the drawings and theoptical or taking lens device will be referred to as a taking lensdevice. A taking lens device optically takes in an image of a subjectthrough an optical system and then outputs the image as an electricalsignal. A taking lens device is used as a main component of a camerawhich is employed to shoot a still or a moving picture of a subject, forexample, a digital still camera, a digital video camera, or a camerathat is incorporated in or externally fitted to a device such as adigital video unit, a personal computer, a mobile computer, a portabletelephone, or a personal digital assistant (PDA). A digital camera alsoincludes a memory to store the image from the image sensor. The memorymay be removable, for example, a disk, or the memory may be permanentlyfixed in the camera. FIG. 19 shows a taking lens device comprising, fromthe object (subject) side, a taking lens system TL that forms an opticalimage of a subject, a plane-parallel plate PL that functions as anoptical low-pass filter or the like, and an image sensor SR thatconverts the optical image formed by the taking lens system TL into anelectrical signal. FIG. 20 shows a zoom lens system ZL, an opticallow-pass filter PL, an image sensor SR, processing circuits PC thatwould include any electronics needed to process the image, and a memoryEM that could be used in a digital camera.

In all the embodiments described hereinafter, the taking lens system TLis built as a zoom lens system comprising a plurality of lens unitswherein zooming is achieved by moving two or more lens units along theoptical axis AX in such a way that their unit-to-unit distances vary.The image sensor SR is realized, for example, with a solid-state imagesensor such as a CCD or CMOS (complementary metal-oxide semiconductor)sensor having a plurality of pixels and, by this image sensor SR, theoptical image formed by the zoom lens system is converted into anelectrical signal. The optical image formed by the zoom lens system hasits spatial frequency characteristics adjusted by being passed throughthe low-pass filter PL that has predetermined cut-off frequencycharacteristics that are determined by the pixel pitch of the imagesensor SR. This helps minimize so-called aliasing noise that appearswhen the optical image is converted into an electrical signal. Thesignal produced by the image sensor SR is subjected, as required, topredetermined digital image processing, image compression, and otherprocessing, and is then recorded as a digital image signal in a memory(such as a semiconductor memory or an optical disk) or, if required,transmitted to another device by way of a cable or after being convertedinto an infrared signal.

FIGS. 1 to 9 are lens arrangement diagrams of the zoom lens system usedin a first to a ninth embodiment, respectively, of the presentinvention, each showing the lens arrangement at the wide-angle end W inan optical sectional view. In each lens arrangement diagram, an arrow mj(where j=1, 2, . . . ) schematically indicates the movement of the j-thlens unit Grj (where j=1, 2, . . . ) and others during zooming from thewide-angle end W to the telephoto end T. Moreover, in each lensarrangement diagram, ri (where i=1, 2, 3, . . . ) indicates the i-thsurface from the object side, and a surface ri marked with an asterisk(*) is an aspherical surface. Di (where i=1, 2, 3, . . . ) indicates thei-th axial distance from the object side, though only those which varywith zooming, called variable distances, are shown here.

In all the embodiments, the zoom lens system comprises at least, fromthe object side, a first lens unit Gr1 having a negative optical power,a second lens unit Gr2 having a negative optical power, and a third lensunit Gr3 having a positive optical power, and achieves zooming byvarying the distances between these lens units. In addition, designedfor a camera (for example, a digital camera) provided with a solid-stateimage sensor (for example, a CCD), the zoom lens system also has a glassplane-parallel plate PL, which functions as an optical low-pass filter,disposed on the image-plane side thereof. In all of the embodiments, thefirst lens unit Gr1 and the glass plane-parallel plate PL are keptstationary during zooming, and the third lens unit Gr3 includes anaperture stop ST at the object-side end thereof.

In the first to the eighth embodiments, the zoom lens system is built asa four-unit zoom lens of a negative-negative-positive-positiveconfiguration. In the ninth embodiment, the zoom lens system is built asa three-unit zoom lens of a negative-negative-positive configuration. Inthe first to the fifth embodiments, during zooming from the wide-angleend W to the telephoto end T, the second lens unit Gr2 first movestoward the image side and then makes a U-turn to go on to move towardthe object side, the third lens unit Gr3 moves toward the object side,and the fourth lens unit Gr4 moves toward the image side. In the sixthto the eighth embodiments, during zooming from the wide-angle end W tothe telephoto end T, the second lens unit Gr2 first moves toward theimage side and then makes a U-turn to go on to move toward the objectside, and the third lens unit Gr3 moves toward the object side, but thefourth lens unit Gr4, i.e. the last lens unit, remains stationarytogether with the glass plane-parallel plate PL. In the ninthembodiment, during zooming from the wide-angle end W to the telephotoend T, the second lens unit Gr2 first moves toward the image side andthen makes a U-turn to go on to move toward the object side, and thethird lens unit Gr3 moves toward the object side.

In all of the embodiments, the first and second lens units Gr1, Gr2 aregiven negative optical powers. This makes it easy to build aretrofocus-type arrangement. In a digital camera, the taking lens systemTL needs to be telecentric toward the image side and, by building aretrofocus-type arrangement with the negatively-powered first and secondlens units Gr1, Gr2, it is possible to make the entire optical systemtelecentric easily. Moreover, by distributing the negative optical powerneeded in a retrofocus-type arrangement between the two lens units Gr1,Gr2, it is possible to keep the first lens unit Gr1 stationary duringzooming. Keeping the first lens unit Gr1 stationary is advantageous interms of lens barrel design, so that it is possible to simplify the lensbarrel construction and thereby reduce the cost of the zoom lens system.

In the first, the second, and the sixth to the ninth embodiments, thefirst lens unit Gr1 comprises a single lens element. By comprising thefirst lens unit Gr1 as a single lens element, it is possible to reducethe cost of the zoom lens system by reducing the number of itsconstituent lens element. Moreover, comprising the first lens unit Gr1out of a single lens element helps increase flexibility in the design oflens barrels so that it is possible to simplify the lens barrelconstruction and thereby reduce the cost of the zoom lens system. On theother hand, in the third to the fifth embodiments, the first lens unitGr1 comprises two lens elements. This makes correction of relativedecentered aberration possible and is thus advantageous in terms ofoptical performance.

In all of the embodiments, it is preferable that the zoom lens system,starting with either a negative-negative-positive or anegative-negative-positive-positive configuration, fulfill theconditions described one by one below. Needless to say, those conditionsmay be fulfilled singly to achieve the effects and advantages associatedwith the respective conditions fulfilled, but fulfilling as many of themas possible is further preferable in terms of optical performance,miniaturization, and other aspects.

It is preferable that conditional formula (1) below be fulfilled.

0.5<f1/f2<5  (1)

wherein

f1 represents the focal length of the first lens unit Gr1; and

f2 represents the focal length of the second lens unit Gr2.

Conditional formula (1) defines the preferable ratio of the focal lengthof the first lens unit Gr1 to that of the second lens unit Gr2. If thelower limit of conditional formula (1) were to be transgressed, thefocal length of the first lens unit Gr1 would be too short. This wouldcause such a large distortion (especially a negative distortion on thewide-angle side) that it would be impossible to secure satisfactoryoptical performance. By contrast, if the upper limit of conditionalformula (1) would be transgressed, the focal length of the first lensunit Gr1 would be too long. This would make the negative optical powerof the first lens unit Gr1 so weak that the first lens unit Gr1 wouldneed to be made larger in diameter, which is undesirable in terms ofminiaturization.

It is preferable that conditional formula (2) below be fulfilled.

1.5<|f12/fw|<4  (2)

where

f12 represents the composite focal length of the first and second lensunits Gr1, Gr2 at the wide-angle end W; and

fw represents the focal length of the entire optical system at thewide-angle end W.

Conditional formula (2) defines the preferable condition to be fulfilledby the composite focal length of the first and second lens units Gr1,Gr2 at the wide-angle end W. If the upper limit of conditional formula(2) were to be transgressed, the composite focal length of the first andsecond lens units Gr1, Gr2 would be too long, and thus the total lengthof the entire optical system would be too long. Moreover, the compositenegative power of the first and second lens units Gr1, Gr2 would be soweak that these lens units would need to be made larger in externaldiameter. Thus, it would be impossible to make the zoom lens systemcompact. By contrast, if the lower limit of conditional formula (2) wereto be transgressed, the composite focal length of the first and secondlens units Gr1, Gr2 would be too short. This would cause such a largenegative distortion in the first and second lens units Gr1, Gr2 at thewide-angle end W that it would be difficult to correct the distortion.

It is preferable that conditional formula (3) below be fulfilled, and itis further preferably fulfilled together with conditional formula (2)noted previously.

0.058<(tan ωw)² ×fw/TLw<0.9  (3)

where

tan ωw represents the half view angle at the wide-angle end W;

fw represents the focal length of the entire optical system at thewide-angle end W; and

TLw represents the total length (i.e. the distance from the first vertexto the image plane) at the wide-angle end W.

Conditional formula (3) defines the preferable relation between the viewangle and the total length at the wide-angle end W. If the upper limitof conditional formula (3) were to be transgressed, the optical power ofthe individual lens units would be too strong, and thus it would bedifficult to correct the aberration that occurs therein. By contrast, ifthe lower limit of conditional formula (3) were to be transgressed, thetotal length would be too long, which is undesirable in terms ofminiaturization.

It is preferable that conditional formula (4) below be fulfilled, and itis further preferably fulfilled together with conditional formula (2)noted previously.

10<TLw×Fnt/(fw×tan ωw)<50  (4)

where

TLw represents the total length (i.e., the distance from the firstvertex to the image plane) at the wide-angle end W;

Fnt represents the f-number (FNO) at the telephoto end T;

fw represents the focal length of the entire optical system at thewide-angle end W; and

tan ωw represents the half view angle at the wide-angle end W.

Conditional formula (4) defines the preferable relation between thetotal length at the wide-angle end W and the f-number at the telephotoend T. If the upper limit of conditional formula (4) were to betransgressed, the total length at the wide-angle end W would be toolong, which is undesirable in terms of miniaturization. By contrast, ifthe lower limit of conditional formula (4) were to be transgressed, thef-number at the telephoto end T would be too low, and thus it would bedifficult to correct the spherical aberration that would occur in thethird lens unit Gr3 in that zoom position.

It is preferable that the third lens unit Gr3 comprises, as in the firstto the fifth and the ninth embodiments, of at least two positive lenselements and one negative lens element. Moreover, it is furtherpreferable that, as in all of the embodiments, the third lens unit Gr3have an aspherical surface at the image-side end thereof. Let themaximum effective optical path radius of an aspherical surface be Ymax,and let the height in a direction perpendicular to the optical axis beY. Then, it is preferable that the aspherical surface disposed at theimage-side end of the third lens unit Gr3 fulfill conditional formula(5) below at Y=0.7Ymax, and further preferably for any height Y in therange 0.1Ymax≦Y≦0.7Ymax.

−0.6<(|X|−X0|)/[C0·(N′−N)·f3]<0  (5)

where

X represents the surface shape (mm) of the aspherical surface (i.e. thedisplacement along the optical axis at the height Y in a directionperpendicular to the optical axis of the aspherical surface);

X0 represents the surface shape (mm) of the reference spherical surfaceof the aspherical surface (i.e. the displacement along the optical axisat the height Y in a direction perpendicular to the optical axis of thereference spherical surface);

C0 represents the curvature (mm⁻¹) of the reference spherical surface ofthe aspherical surface;

N represents the refractive index for the d-line of the object-sidemedium of the aspherical surface;

N′ represents the refractive index for the d-line of the image-sidemedium of the aspherical surface; and

f3 represents the focal length (mm) of the third lens unit Gr3.

Here, the surface shape X of the aspherical surface, and the surfaceshape X0 of its reference spherical surface are respectively given byformulae (AS) and (RE) below.

X=(C0·Y ²)/(1+{square root over (1−ε·C0² ·Y ²)})+Σ( Ai·Y ^(i))   (AS)

X0=(C0·Y ²)/(1+{square root over (1−C0² ·Y ²)}  (RE)

where

C0 represents the curvature (mm⁻¹) of the reference spherical surface ofthe aspherical surface;

Y represents the height in a direction perpendicular to the opticalaxis;

ε represents the quadric surface parameter; and

Ai represents the aspherical surface coefficient of order i.

Conditional formula (5) dictates that the aspherical surface be soshaped as to weaken the positive power within the third lens unit Gr3,and thus defines the preferable condition to be fulfilled to ensureproper correction of spherical aberration from the middle-focal-lengthregion M to the telephoto end T. If the upper limit of conditionalformula (5) were to be transgressed, spherical aberration would inclinetoo much toward the under side. By contrast, if the lower limit ofconditional formula (5) were to be transgressed, spherical aberrationwould incline too much toward the over side.

It is preferable that, as in all of the embodiments, the zoom unitdisposed closest to the image plane have a positive power, and it ispreferable that the zoom unit having this positive power comprises atleast one positive lens element. In cases, as in the first, the fourth,and the sixth to the eighth embodiments, where this zoom unit having theabove-mentioned positive power comprises a single positive lens element,it is preferable that this positive lens element fulfill conditionalformula (6) below.

0.05<(CR1−CR2)/(CR1+CR2)<5  (6)

where

CR1 represents the radius of curvature of the object-side surface; and

CR2 represents the radius of curvature of the image-side surface.

Conditional formula (6) defines the preferable shape of the positivelens element included in the zoom unit disposed closest to the imageplane. If the upper limit of conditional formula (6) were to betransgressed, the surface of this positive lens element facing theobject would be highly concave, and therefore, to avoid interferencewith the lens unit disposed on the object side of that surface, it wouldbe necessary to secure a wide gap in between. This is undesirable interms of miniaturization. By contrast, if the lower limit of conditionalformula (6) were to be transgressed, the positive optical power of theobject-side surface of the positive lens element would be so strong thatit would be difficult to correct the aberration that would be caused bythat surface.

It is preferable that the first to third lens units Gr1 to Gr3 fulfillconditional formula (7) below.

0.4<|f12/f3|<1.5  (7)

where

f12 represents the composite focal length of the first and second lensunits Gr1, Gr2, at the wide-angle end W; and

f3 represents the focal length (mm) of the third lens unit Gr3.

Conditional formula (7) defines the preferable ratio of the compositefocal length of the first and second lens units Gr1, Gr2 to the focallength of the third lens unit Gr3. If the upper limit of conditionalformula (7) were to be transgressed, the composite focal length of thefirst and second lens units Gr1, Gr2 would be relatively too long. Thus,if the upper limit of conditional formula (7) were to be transgressed,the exit pupil would be located closer to the image plane, and this isnot desirable. As described earlier, in a digital still camera or thelike, the use of a CCD and other factors require that rays striking theimage plane be telecentric, and therefore it is preferable that the exitpupil be located closer to the object. By contrast, if the lower limitof conditional formula (7) were to be transgressed, the composite focallength of the first and second lens units Gr1, Gr2 would be relativelytoo short. Thus, if the lower limit of conditional formula (7) were tobe transgressed, it would be difficult to correct the negativedistortion that would occur in the first and second lens units Gr1, Gr2.

In all of the illustrated embodiments, all of the lens units arecomprised solely of refractive lenses that deflect light incidentthereon by refraction (i.e. lenses of the type that deflect light at theinterface between two media having different refractive indices).However, any of these lens units may include, for example, a diffractivelens that deflects light incident thereon by diffraction, arefractive-diffractive hybrid lens that deflects light incident thereonby the combined effects of refraction and diffraction, a gradient-indexlens that deflects light incident thereon with varying refractiveindices distributed in a medium, or a lens of any other type.

In any of the embodiments, a surface having no optical power (forexample, a reflective, refractive, or diffractive surface) may bedisposed in the optical path so that the optical path is bent before,after, or in the midst of the zoom lens system. Where to bend theoptical path may be determined to suit particular needs. By bending theoptical path appropriately, it is possible to make a camera apparentlyslimmer. It is even possible to build an arrangement in which zooming orthe collapsing movement of a lens barrel does not cause any change inthe thickness of a camera. For example, by disposing a mirror after thefirst lens unit Gr1, which is kept stationary during zooming, so thatthe optical path is bent by 90° by the reflecting surface of the mirror,it is possible to keep the front-to-rear length of the zoom lens systemconstant and thereby make a camera slimmer.

In all of the embodiments, an optical low-pass filter having the shapeof a plane-parallel plate PL is disposed between the last surface of thezoom lens system and the image sensor SR. However, as this low-passfilter, it is also possible to use a birefringence-type low-pass filtermade of quartz or the like having its crystal axis aligned with apredetermined direction, a phase-type low-pass filter that achieves therequired optical cut-off frequency characteristics by exploitingdiffraction, or a low-pass filter of any other type.

PRACTICAL EXAMPLES

Hereinafter, practical examples of the construction of the zoom lenssystem used in taking lens devices embodying the present invention willbe presented in more detail with reference to their construction data,aberration diagrams, and other data. Examples 1 to 9 presented belowcorrespond respectively to the first to ninth embodiments describedhereinbefore, and the lens arrangement diagrams (FIGS. 1 to 9) showingthe lens arrangement of the first to the ninth embodiments apply also toExamples 1 to 9, respectively.

Tables 1 to 9 list the construction data of Examples 1 to 9,respectively. In the construction data of each example, ri (i=1, 2, 3, .. . ) represents the radius of curvature (mm) of the i-th surface fromthe object side, di (i=1, 2, 3, . . . ) represents the i-th axialdistance (mm) from the object side, and Ni (i=1, 2, 3, . . . ) and νi(i=1, 2, 3, . . . ) respectively represent the refractive index (Nd) forthe d-line and the Abbe number (νd) of the i-th optical element from theobject side. A surface whose radius of curvature ri is marked with anasterisk (*) is an aspherical surface, of which the surface shape isdefined by formula (AS) noted earlier. Moreover, in the constructiondata, for each of those axial distances that vary with zooming (i.e.variable aerial distances), three values are given that are, from left,the axial distance at the wide-angle end W (the shortest-focal-lengthend), the axial distance in the middle position M (themiddle-focal-length position), and the axial distance at the telephotoend T (the longest-focal-length end). Also listed are the focal lengthf, (in mm), the f-number FNO, and the view angle (2ω, °) of the entireoptical system in those three focal-length positions W, M, and T, andthe aspherical surface data. Table 10 lists the values of theconditional formulae as actually observed in Examples 1 to 9.

FIGS. 10A-10I, 11A-11I, 12A-12I, 13A-13I, 14A-14I, 15A-15I, 16A-16I,17A-17I, and 18A-18I are aberration diagrams of Examples 1 to 9,respectively. Of these diagrams, FIGS. 10A-10C, 11A-11C, 12A-12C,13A-13C, 14A-14C, 15A-15C, 16A-16C, 17A-17C, and 18A-18C show theaberration observed at the wide-angle end W, FIGS. 10D-10F, 11D-11F,12D-12F, 13D-13F, 14D-14F, 15D-15F, 16D-16F, 17D-17F, and 18D-18F showthe aberration observed in the middle position M, and FIGS. 10G-10I,11G-11I, 12G-12I, 13G-13I, 14G-14I, 15G-15I, 16G-16I, 17G-17I, and18G-18I show the aberration observed at the telephoto end T. Of thesediagrams, FIGS. 10A, 10D, 10G, 11A, 11D, 11G, 12A, 12D, 12G, 13A, 13D,13G, 14A, 14D, 14G, 15A, 15D, 15G, 16A, 16D, 16G, 17A, 17D, 17G, 18A,18D, and 18G show spherical aberration, FIGS. 10B, 10E, 10H, 11B, 11E,11H, 12B, 12E, 12H, 13B, 13E, 13H, 14B, 14E, 14H, 15B, 15E, 15H, 16B,16E, 16H, 17B, 17E, 17H, 18B, 18E, and 18H show astigmatism, and FIGS.10C, 10F, 10I, 11C, 11F, 11I, 12C, 12F, 12I, 13C, 13F, 13I, 14C, 14F,14I, 15C, 15F, 15I, 16C, 16F, 16I, 17C, 17F, 17I, 18C, 18F, and 18I showdistortion. In these diagrams, Y′ represents the maximum image height(mm). In the diagrams showing spherical aberration, a solid line d, adash-and-dot line g, and a dash-dot-dot line c show the sphericalaberration for the d-line, for the g-line, and for the c-line,respectively, and a broken line SC shows the sine condition. In thediagrams showing astigmatism, a broken line DM and a solid line DSrepresent the astigmatism for the d-line on the meridional plane and onthe sagittal plane, respectively. In the diagrams showing distortion, asolid line represents the distortion (%) for the d-line.

TABLE 1 Construction Data of Example 1 f = 4.45˜7.8˜12.7, FNO =2.84˜2.84˜2.90, 2ω = 75.8˜46.8˜28.9 Radius of Axial Refractive AbbeCurvature Distance Index Number r1 = 18.401 d1 = 0.800 N1 = 1.54072 ν1 =47.22 r2 = 5.940 d2 = 3.275˜6.628˜5.000 r3* = −46.268 d3 = 0.800 N2 =1.52200 ν2 = 52.20 r4* = 7.744 d4 = 1.115 r5 = 10.618 d5 = 1.784 N3 =1.84666 ν3 = 23.82 r6 = 29.518 d6 = 14.440˜6.151˜2.201 r7 = ∞(ST) d7 =0.600 r8 = 10.096 d8 = 1.673 N4 = 1.75450 ν4 = 51.57 r9 = 35.493 d9 =0.100 r10 = 6.646 d10 = 2.391 N5 = 1.75450 ν5 = 51.57 r11 = 42.505 d11 =0.436 r12 = 372.791 d12 = 0.800 N6 = 1.84666 ν6 = 23.82 r13 = 5.188 d13= 0.800 r14 = 6.476 d14 = 2.091 N7 = 1.52200 ν7 = 52.20 r15* = 43.112d15 = 1.283˜8.292˜13.780 r16* = −50.000 d16 = 2.639 N8 = 1.75450 ν8 =51.57 r17* = −9.674 d17 = 2.774˜0.700˜0.790 r18 = ∞ d18 = 2.000 N9 =1.51680 ν9 = 64.20 r19 = ∞ Aspherical Surface Data of Surface r3 ε =1.0000, A4 = 0.66858 × 10⁻³, A6 = −0.25227 × 10⁻⁴, A8 = 0.41627 × 10⁻⁶Aspherical Surface Data of Surface r4 ε = 1.0000, A4 = 0.27983 × 10⁻³,A6 = −0.33808 × 10⁻⁴, A8 = 0.43681 × 10⁻⁶ Aspherical Surface Data ofSurface r15 ε = 1.0000, A4 = 0.14395 × 10⁻², A6 = 0.21710 × 10⁻⁴, A8 =0.13202 × 10⁻⁵ Aspherical Surface Data of Surface r16 ε = 1.0000, A4 =−0.39894 × 10⁻³, A6 = −0.41378 × 10^(−4,) A8 = 0.19806 × 10⁻⁵ AsphericalSurface Data of Surface r17 ε = 1.0000, A4 = 0.27510 × 10⁻³, A6 =−0.46341 × 10⁻⁴, A8 = 0.17216 × 10⁻⁵

TABLE 2 Construction Data of Example 2 f = 4.45˜7 8˜12.7, FNO =2.67˜2.90˜2.90, 2ω = 76.9˜46.6˜28.5 Radius of Axial Refractive AbbeCurvature Distance Index Number r1 = 12.628 d1 = 1.000 N1 = 1.58913 ν1 =61.25 r2 = 5.734 d2 = 3.800˜6.823˜4.759 r3* = −17.691 d3 = 0.800 N2 =1.52200 ν2 = 52.20 r4* = 8.550 d4 = 1.669 r5 = 14.585 d5 = 1.500 N3 =1.84666 ν3 = 23.78 r6 = 75.547 d6 = 12.939˜5.191˜1.490 r7 = ∞(ST) d7 =0.600 r8 = 10.478 d8 = 1.730 N4 = 1.78831 ν4 = 47.32 r9 = 48.647 d9 =0.100 r10 = 5.925 d10 = 2.491 N5 = 1.58913 ν5 = 61.25 r11 = 20.627 d11 =0.010 N6 = 1.51400 ν6 = 42.83 r12 = 20.627 d12 = 0.700 N7 = 1.84666 ν7 =23.78 r13 = 4.609 d13 = 0.632 r14 = 4.757 d14 = 2.626 N8 = 1.52200 ν8 =52.20 r15* = 14.654 d15 = 1.439˜7.835˜13.100 r16* = −50.000 d16 = 1.000N9 = 1.58340 ν9 = 30.23 r17* = 70.535 d17 = 0.591 r18 = −94.053 d18 =1.802 N10 = 1.78590 ν10 = 43.93 r19 = −8.643 d19 = 2.371˜0.700˜1.200 r20= ∞ d20 = 2.000 N11 = 1.51680 ν11 = 64.20 r21 = ∞ Aspherical SurfaceData of Surface r3 ε = 1.0000, A4 = 0.56623 × 10⁻³, A6 = −0.23264 ×10⁻⁴, A8 = 0.30123 × 10⁻⁶ Aspherical Surface Data of Surface r4 ε =1.0000, A4 = 0.43838 × 10⁻⁴, A6 = −0.28329 × 10⁻⁴, A8 = 0.33275 × 10⁻⁶Aspherical Surface Data of Surface r15 ε = 10000, A4 = 0.21324 × 10⁻²,A6 = 0.32366 × 10⁻⁴, A8 = 0.53566 × 10⁻⁵ Aspherical Surface Data ofSurface r16 ε = 1.0000, A4 = 0.95453 × 10⁻³, A6 = −0.13928 × 10⁻³, A8 =0.43729 × 10⁻⁵ Aspherical Surface Data of Surface r17 ε = 1.0000, A4 =0.20120 × 10⁻², A6 = −0.13956 × 10⁻³, A8 = 0.38295 × 10⁻⁵

TABLE 3 Construction Data of Example 3 f = 4.45˜7.8˜12.7, FNO =2.70˜2.84˜2.89, 2ω = 76.6˜46.4˜29.1 Radius of Axial Refractive AbbeCurvature Distance Index Number r1 = 11.274 d1 = 1.000 N1 = 1.74330 ν1 =49.22 r2 = 5.143 d2 = 3.500 r3* = 302.871 d3 = 1.800 N2 = 1.52200 ν2 =52.20 r4* = −39.780 d4 = 1.500˜3.907˜1.412 r5 = −20.000 d5 = 0.800 N3 =1.63854 ν3 = 55.45 r6 = 10.669 d6 = 0.800 r7 = 12.450 d7 = 1.550 N4 =1.84666 ν4 = 23.78 r8 = 48.662 d8 = 10.824˜3.774˜1.000 r9 = ∞(ST) d9 =0.600 r10 = 11.059 d10 = 1.807 N5 = 1.77250 ν5 = 49.77 r11 = 137.002 d11= 0.100 r12 = 7.339 d12 = 2.800 N6 = 1.75450 ν6 = 51.57 r13 = −37.431d13 = 0.010 N7 = 1.51400 ν7 = 42.83 r14 = −37.431 d14 = 0.712 N8 =1.84666 ν8 = 23.78 r15 = 6.744 d15 = 1.282 r16 = 9.773 d16 = 1.500 N9 =1.52200 ν9 = 52.20 r17* = 33.228 d17 = 1.112˜7.313˜12.854 r18* = 22.508d18 = 1.000 N10 = 1.58340 ν10 = 30.23 r19* = 8.706 d19 = 0.773 r20 = 53706 d20 = 1.801 N11 = 1.78590 ν11 = 43.93 r21 = −10.576 d21 =2.530˜0.971˜0.700 r22 = ∞ d22 = 2.000 N12 = 1.51680 ν12 = 64.20 r23 = ∞Aspherical Surface Data of Surface r3 ε = 1.0000, A4 = 0.28635 × 10⁻³,A6 = 0.15667 × 10⁻⁴, A8 = −0.57168 × 10⁻⁶ Aspherical Surface Data ofSurface r4 ε = 1.0000, A4 = −0.17053 × 10⁻³, A6 = 0.80129 × 10⁻⁵, A8 =−0.94476 × 10⁻⁶ Aspherical Surface Data of Surface r17 ε = 1.0000, A4 =0.14359 × 10⁻², A6 = 0.19756 × 10⁻⁴, A8 = 0.24320 × 10⁻⁵ AsphericalSurface Data of Surface r18 ε = 1.0000, A4 = −0.14772 × 10⁻², A6 = −028230 × 10⁻⁴, A8 = 0.39925 × 10⁻⁵ Aspherical Surface Data of Surface r19ε = 1.0000, A4 = −0.12532 × 10⁻², A6 = −0.15384 × 10⁻⁴, A8 = 0.28984 ×10⁻⁵

TABLE 4 Construction Data of Example 4 f = 4.45˜7.8˜12.7, FNO =2.88˜2.81˜2.90, 2ω = 76.7˜46˜28.9 Radius of Axial Refractive AbbeCurvature Distance Index Number r1 = 12.938 d1 = 1.000 N1 = 1.74330 ν1 =49.22 r2 = 5.796 d2 = 3.500 r3* = 44.528 d3 = 1.800 N2 = 1.52200 ν2 =52.20 r4* = −104.899 d4 = 1.553˜3.953˜1.483 r5 = −20.000 d5 = 0.800 N3 =1.63854 ν3 = 55.45 r6 = 10.131 d6 = 1.135 r7 = 13.404 d7 = 2.000 N4 =1.84666 ν4 = 23.78 r8 = 61.168 d8 = 10.984˜3.778˜1.000 r9 = ∞(ST) d9 =0.600 r10 = 11.382 d10 = 2.046 N5 = 1.77250 ν5 = 49.77 r11 = −52.132 d11= 0.100 r12 = 7.001 d12 = 2.783 N6 = 1.75450 ν6 = 51.57 r13 = −24.543d13 = 0.010 N7 = 1.51400 ν7 = 42 83 r14 = −24.543 d14 = 0.700 N8 =1.84666 ν8 = 23.78 r15 = 6.105 d15 = 1.361 r16* = −22.829 d16 = 1.641 N9= 1.52200 ν9 = 52.20 r17* = −17.058 d17 = 1.128˜7.052˜12.841 r18* =−50.000 d18 = 2.800 N10 = 1.74330 ν10 = 49.22 r19 = −10 303 d19 =2.359˜1.241˜0.700 r20 = ∞ d20 = 2.000 N11 = 1.51680 ν11 = 64.20 r21 = ∞Aspherical Surface Data of Surface r3 ε = 1.0000, A4 = 0.19527 × 10⁻³,A6 = 0.57342 × 10⁻⁸, A8 = −0.20853 × 10⁻⁶ Aspherical Surface Data ofSurface r4 ε = 1.0000, A4 = −0.17096 × 10⁻³, A6 = −0.10072 × 10⁻⁴, A8 =−0.10753 × 10⁻⁶ Aspherical Surface Data of Surface r16 ε = 1.0000, A4 =−0.13142 × 10⁻², A6 = 0.94352 × 10⁻⁴, A8 = −0.12279 × 10⁻⁵ AsphericalSurface Data of Surface r17 ε = 1.0000, A4 = 0.11300 × 10⁻³, A6 =0.11926 × 10⁻³, A8 = −0.60390 × 10⁻⁷ Aspherical Surface Data of Surfacer18 ε = 1.0000, A4 = −0.50806 × 10⁻³, A6 = 0.29779 × 10⁻⁵, A8 = −0.38526× 10⁻⁷

TABLE 5 Construction Data of Example 5 f = 4.8˜9.7˜15.5, FNO =2.83˜2.85˜3.01, 2ω = 72.6˜36.8˜23.5 Radius of Axial Refractive AbbeCurvature Distance Index Number r1 = 11.104 d1 = 0.800 N1 = 1.74330 ν1 =49.22 r2 = 6.378 d2 = 2.300 r3* = 14.802 d3 = 1.800 N2 = 1.52200 ν2 =52.20 r4* = 20.396 d4 = 2.430˜5.010˜4.866 r5 = −20.000 d5 = 0.800 N3 =1.63854 ν3 = 55.45 r6 = 9.907 d6 = 0.800 r7 = 10.952 d7 = 1.500 N4 =1.84666 ν4 = 23.78 r8 = 27.854 d8 = 11.584˜3.183˜1.000 r9 = ∞(ST) d9 =0.600 r10 = 16.003 d10 = 1.787 N5 = 1.77250 ν5 = 49.77 r11 = −34.803 d11= 0.100 r12 = 6.218 d12 = 2.784 N6 = 1.75450 ν6 = 51.57 r13 = −93.239d13 = 0.010 N7 = 1.51400 ν7 = 42.83 r14 = −93.241 d14 = 0.700 N8 =1.84666 ν8 = 23.78 r15 = 5.710 d15 = 1.002 r16 = 11.201 d16 = 1.500 N9 =1.52200 ν9 = 52.20 r17* = 16.808 d17 = 1.180˜7.784˜13.237 r18* = −50.000d18 = 1.000 N10 = 1.58340 ν10 = 30.23 r19* = −55.066 d19 = 0.515 r20 =37.772 d20 = 1.500 N11 = 1.78590 ν11 = 43.93 r21 = −20.359 d21 =1.609˜0.825˜0.700 r22 = ∞ d22 = 2.000 N12 = 1.51680 ν12 = 64.20 r23 = ∞Aspherical Surface Data of Surface r3 ε = 1.0000, A4 = −0.68378 × 10⁻⁴,A6 = 0.91459 × 10⁻⁵, A8 = −0.17059 × 10⁻⁶ Aspherical Surface Data ofSurface r4 ε = 1.0000, A4 = −0.30623 × 10⁻³, A6 = 0.77956 × 10⁻⁵, A8 =−0.26508 × 10⁻⁶ Aspherical Surface Data of Surface r17 ε = 1.0000, A4 =0.15313 × 10⁻², A6 = 0.48360 × 10⁻⁴, A8 = 0.33469 × 10⁻⁵ AsphericalSurface Data of Surface r18 ε = 1.0000, A4 = 0.33814 × 10⁻², A6 =−0.12472 × 10⁻³, A8 = 0.45839 × 10⁻⁵ Aspherical Surface Data of Surfacer19 ε = 1.0000, A4 = 0.39759 × 10⁻², A6 = −0.12370 × 10⁻³, A8 = 0.47201× 10⁻⁵

TABLE 6 Construction Data of Example 6 f = 3.0˜5.2˜8.6, FNO =2.30˜3.18˜4.10, 2ω = 76.7˜46.2˜28.2 Radius of Axial Refractive AbbeCurvature Distance Index Number r1 = 18.376 d1 = 0.750 N1 = 1.75450 ν1 =51.57 r2 = 5.908 d2 = 2.654˜5.660˜2.654 r3* = −38.428 d3 = 0.750 N2 =1.52510 ν2 = 56.38 r4* = 3.454 d4 = 1.298 r5 = 6.786 d5 = 2.177 N3 =1.58340 ν3 = 30.23 r6 = −250.470 d6 = 9.631˜2.374˜1.000 r7 = ∞(ST) d7 =0.600 r8 = 4.468 d8 = 4.230 N4 = 1.76822 ν4 = 46.58 r9 = −5.283 d9 =0.010 N5 = 1.51400 ν5 = 42.83 r10 = −5.283 d10 = 0.750 N6 = 1.84666 ν6 =23.82 r11* = 12.622 d11 = 2.573˜6.824˜11.205 r12 = −17.607 d12 = 1.478N7 = 1.52510 ν7 = 56.38 r13* = −5.316 d13 = 0.500 r14 = ∞ d14 = 3.400 N8= 1.51680 ν8 = 64.20 r15 = ∞ Aspherical Surface Data of Surface r3 ε =1.0000, A4 = −0.22743 × 10⁻³, A6 = 0.81018 × 10⁻⁴, A8 = −0.11992 × 10⁻⁴Aspherical Surface Data of Surface r4 ε = 1.0000, A4 = −0.34914 × 10⁻²,A6 = −0.12871 × 10⁻³, A8 = −0.99555 × 10⁻⁵ Aspherical Surface Data ofSurface r11 ε = 1.0000, A4 = 0.47689 × 10⁻², A6 = 0.18896 × 10⁻³, A8 =0.77520 × 10⁻⁴ Aspherical Surface Data of Surface r13 ε = 1.0000, A4 =0.26471 × 10⁻², A6 = −0.51516 × 10⁻⁴, A8 = 0.18942 × 10⁻⁵

TABLE 7 Construction Data of Example 7 f = 2.5˜4.8˜7.3, FNO =2.37˜3.33˜4.10, 2ω = 72.9˜40.4˜26.7 Radius of Axial Refractive AbbeCurvature Distance Index Number r1 = 16.241 d1 = 0.800 N1 = 1.75450 ν1 =51.57 r2 = 5.499 d2 = 3.085˜5.394˜3.085 r3* = 23.072 d3 = 1.000 N2 =1.52510 ν2 = 56.38 r4* = 3.156 d4 = 1.390 r5 = 5.079 d5 = 1.653 N3 =1.84666 ν3 = 23.82 r6 = 7.886 d6 = 9.655˜3.023˜1.879 r7 = ∞(ST) d7 =0.600 r8 = 4.268 d8 = 3.824 N4 = 1.73299 ν4 = 52.32 r9 = −5.710 d9 =0.010 N5 = 1.51400 ν5 = 42.83 r10 = −5.710 d10 = 0.750 N6 = 1.84666 ν6 =23.82 r11* = 27.698 d11 = 1.576˜5.899˜9.351 r12 = −12.089 d12 = 2.546 N7= 1.52510 ν7 = 56.38 r13* = −4.510 d13 = 0.500 r14 = ∞ d14 = 3.400 N8 =1.51680 ν8 = 64.20 r15 = ∞ Aspherical Surface Data of Surface r3 ε =1.0000, A4 0.11334 × 10⁻², A6 = 0.83390 × 10⁻⁴, A8 = −0 24186 × 10⁻⁴Aspherical Surface Data of Surface r4 ε 1.0000, A4 = −0.14398 × 10⁻², A6= −0.68030 × 10⁻⁴, A8 = −0.49071 × 10⁻⁴ Aspherical Surface Data ofSurface r11 ε = 1.0000, A4 = 0.43753 × 10⁻², A6 = 0.23651 × 10⁻³, A8 =0.47406 × 10⁻⁴ Aspherical Surface Data of Surface r13 ε = 1.0000, A4 =0.35646 × 10⁻², A6 = −0.42883 × 10^(−4,) A8 = 0.14875 × 10⁻⁵

TABLE 8 Construction Data of Example 8 f = 1.6˜3.0˜4.6, FNO =2.44˜3.37˜4.10, 2ω = 76.4˜43.8˜28.8 Radius of Axial Refractive AbbeCurvature Distance Index Number r1 = 7.967 d1 = 0.800 N1 = 1.75450 ν1 =51.57 r2 = 3.205 d2 = 2.923˜4.841˜3.019 r3* = 14.015 d3 = 1.000 N2 =1.52510 ν2 = 56.38 r4* = 2.338 d4 = 2.084 r5 = 5.334 d5 = 3.470 N3 =1.84666 ν3 = 23.82 r6 = 8.028 d6 = 7.717˜2.047˜1.000 r7 = ∞(ST) d7 =0.600 r8 = 4.296 d8 = 3.644 N4 = 1.76050 ν4 = 50.55 r9 = −4.200 d9 =0.010 N5 = 1.51400 ν5 = 42.83 r10 = −4.200 d10 = 0.750 N6 = 1.84666 ν6 =23.82 r11* = −159.225 d11 = 0.897˜4.648˜7.518 r12 = −8.166 d12 = 2.207N7 = 1.52510 ν7 = 56.38 r13* = −3.963 d13 = 0.500 r14 = ∞ d14 = 3.400 N8= 1.51680 ν8 = 64.20 r15 = ∞ Aspherical Surface Data of Surface r3 ε =1.0000, A4 = 0.19149 × 10⁻², A6 = 0.14015 × 10⁻², A8 = −0.37347 × 10⁻³,A10 = 0.31010 × 10⁻⁴ Aspherical Surface Data of Surface r4 ε = 1.0000,A4 = −0.67645 × 10⁻², A6 = −0.60143 × 10⁻⁴, A8 = −0.46412 × 10⁻³Aspherical Surface Data of Surface r11 ε = 1.0000, A4 = 0.37565 × 10⁻²,A6 = 0.66871 × 10⁻³, A8 = −0.80434 × 10⁻⁴ Aspherical Surface Data ofSurface r13 ε = 1.0000, A4 = 0.52954 × 10⁻², A6 = −0.75580 × 10⁻³, A8 =0.15734 × 10⁻³

TABLE 9 Construction Data of Example 9 f = 4.5˜7.8˜12.7, FNO =3.24˜3.09˜4.13, 2ω = 76.4˜47.9˜29.6 Radius of Axial Refractive AbbeCurvature Distance Index Number r1 = 21.240 d1 = 1.200 N1 = 1.75450 ν1 =51.57 r2 = 5.872 d2 = 3.000˜8.500˜4.979 r3* = 8.946 d3 = 1.000 N2 =1.62112 ν2 = 57.62 r4* = 4.431 d4 = 2.156 r5 = 7.067 d5 = 2.000 N3 =1.84666 ν3 = 23.82 r6 = 9.677 d6 = 11.453˜2.003˜1.000 r7 = ∞(ST) d7 =0.600 r8* = 5.559 d8 = 1.675 N4 = 1.57965 ν4 = 60.49 r9 = 13.046 d9 =0.100 r10 = 6.192 d10 = 2.500 N5 = 1.48749 ν5 = 70.44 r11 = −11.918 d11= 0.203 r12 = −14.208 d12 = 3.421 N6 = 1.79850 ν6 = 22.60 r13* = 21.481d13 = 0.780 r14 = 14.579 d14 = 4.000 N7 = 1.75450 ν7 = 51.57 r15* =12.388 d15 = 1.898˜5.848˜10.372 r16 = ∞ d16 = 2.000 N8 = 1.51680 ν8 =64.20 r17 = ∞ Aspherical Surface Data of Surface r3 ε = 1.0000, A4 =0.13577 × 10⁻², A6 = −0.10949 × 10⁻³, A8 = 0.37797 × 10⁻⁵ AsphericalSurface Data of Surface r4 ε = 1.0000, A4 = 0.65141 × 10⁻³, A6 =−0.18413 × 10⁻³, A8 = 0.34984 × 10⁻⁵ Aspherical Surface Data of Surfacer8 ε = 1.0000, A4 = −0.30607 × 10⁻³, A6 = −0.12679 × 10⁻⁴, A8 = −0.66500× 10⁻⁶ Aspherical Surface Data of Surface r13 ε = 1.0000, A4 = 0.28699 ×10⁻², A6 = 0.29442 × 10⁻⁵, A8 = 0.14242 × 10⁻⁴ Aspherical Surface Dataof Surface r15 ε = 1.0000, A4 = −0.73341 × 10⁻³, A6 = 0.14643 × 10⁻³, A8= −0.36100 × 10⁻⁵

TABLE 10 Actual Values of Conditional Formulae (3) (4) (5) Y = 0.7 Ymax(6) (1) (2) (tanωw)² · TLw□Fnt/ (|X| − |X0|)/ (CR1 − CR2)/ (7) Ex. f1/f2|f12/fw| fw/TLw (fw · tanωw) [C0(N′ − N)f3] (CR1 + CR2) |f12/f3| 1 2.6202.482 0.065 34.43 −0.267 0.676 1.024 2 1.434 2.416 0.068 33.65 −0.094 —1.042 3 1.426 2.140 0.068 33.71 −0.199 — 0.974 4 1.131 2.270 0.067 34.19−0.023 0.658 1.017 5 0.773 2.315 0.066 33.59 −0.091 — 1.203 6 1.4432.268 0.059 55.29 −0.033 0.054 0.873 7 1.337 2.260 0.043 69.95 −0.0900.457 0.817 8 1.269 2.206 0.032 101.59 −0.069 0.347 0.590 9 3.909 1.8120.071 46.08 0.002 — 1.023

What is claimed is:
 1. An optical device comprising: a zoom lens system,comprising a plurality of lens units, which achieves zooming by varyingunit-to-unit distances; and an image sensor for converting an opticalimage formed by the zoom lens system into an electrical signal, whereinthe zoom lens system comprises at least, from an object side thereof toan image side thereof, a first lens unit having a negative opticalpower, a second lens unit having a negative optical power, and a thirdlens unit having a positive optical power; wherein the third lens unithas an aspherical surface at the image side thereof; and wherein thefollowing conditional formulae are fulfilled:−0.6<(|X|−|X0|)/[C0·(N′−N)·f3]<0 0.1Ymax≦Y≦0.7Ymax wherein X representsa surface shape of the aspherical surface; X0 represents a surface shapeof a reference spherical surface of the aspherical surface; C0represents a curvature of the reference spherical surface of theaspherical surface; N represents a refractive index for a d-line of theobject-side medium of the aspherical surface; N′ represents therefractive index for the d-line of the image-side medium of theaspherical surface; f3 represents a focal length of the third lens unit;Ymax represents a maximum effective optical path of an asphericalsurface; and Y represents a height in a direction perpendicular to anoptical axis.
 2. An optical device comprising: a zoom lens system,comprising a plurality of lens units, which achieves zooming by varyingunit-to-unit distances; and an image sensor for converting an opticalimage formed by the zoom lens system into an electrical signal, whereinthe zoom lens system comprises at least, from an object side thereof toan image side thereof, a first lens unit having a negative optical powerand provided at the most object side of the zoom lens system, a secondlens unit having a negative optical power, and a third lens unit havinga positive optical power, and wherein the following conditional formulais fulfilled: 0.5<f1/f2<5 wherein f1 represents a focal length of thefirst lens unit; and f2represents a focal length of the second lensunit.
 3. An optical device comprising: a zoom lens system, comprising aplurality of lens units, which achieves zooming by varying unit-to-unitdistances; and an image sensor for converting an optical image formed bythe zoom lens system into an electrical signal, wherein the zoom lenssystem comprises at least, from an object side thereof to an image sidethereof, a first lens unit having a negative optical power, a secondlens unit having a negative optical power, and a third lens unit havinga positive optical power; and wherein the following conditional formulaeare fulfilled: 1.5<|fl2/fw|<4 0.058<(tan ωw)² ×fw/TLw<0.9 wherein fl2represents a composite focal length of the first and the second lensunits at a wide-angle end; tan ωw represents a half view angle at awide-angle end; fw represents a focal length of an entire optical systemat the wide-angle end; and TLw represents a distance from a first vertexto an image plane at the wide-angle end.
 4. An optical devicecomprising: a zoom lens system, comprising a plurality of lens units,which achieves zooming by varying unit-to-unit distances; and an imagesensor for converting an optical image formed by the zoom lens systeminto an electrical signal, wherein the zoom lens system comprises atleast, from an object side thereof to an image side thereof, a firstlens unit having a negative optical power, a second lens unit having anegative optical power, and a third lens unit having a positive opticalpower; and wherein the following conditional formulae is fulfilled:1.5<|fl2/fw|<4 10<TLw×Fnt/(fw×tan ωw)<50 where TLw represents a distancefrom a first vertex to an image plane at a wide-angle end; Fntrepresents an f-number at a telephoto end; fl2 represents a compositefocal length of the first and the second lens units at the wide-angleend; fw represents a focal length of an entire optical system at thewide-angle end; and tan ωw represents a half view angle at thewide-angle end.
 5. An optical device comprising: a zoom lens system,comprising a plurality of lens units, which achieves zooming by varyingunit-to-unit distances; and an image sensor for converting an opticalimage formed by the zoom lens system into an electrical signal, whereinthe zoom lens system comprises at least, from an object side thereof toan image side thereof, a first lens unit having a negative optical powerand provided at the most object side of the zoom lens system, a secondlens unit having a negative optical power, and a third lens unit havinga positive optical power, and wherein the lens unit closest to the imageside has a positive optical power, said lens unit is comprised of atleast one positive lens element and the positive lens element fulfillsthe following conditional formula: 0.05<(CR1−CR2)/(CR1+CR2)<5 whereinCR1 represents a radius of curvature of the object-side surface; and CR2represents a radius of curvature of the image-side surface.
 6. Anoptical device comprising: a zoom lens system, comprising a plurality oflens units, which achieves zooming by varying unit-to-unit distances;and an image sensor for converting an optical image formed by the zoomlens system into an electrical signal, wherein the zoom lens systemcomprises at least, from an object side thereof to an image sidethereof, a first lens unit having a negative optical power, a secondlens unit having a negative optical power, and a third lens unit havinga positive optical power; and wherein the following conditional formulais fulfilled: 04<|fl2/f3|<1.5 where fl2 represents a composite focallength of the first and the second lens units at a wide-angle end; andf3 represents a focal length of the third lens unit.
 7. An opticaldevice comprising: a zoom lens system, comprising a plurality of lensunits, which achieves zooming by varying unit-to-unit distances; and animage sensor for converting an optical image formed by the zoom lenssystem into an electrical signal, wherein the zoom lens system comprisesat least, from an object side thereof to an image side thereof, a firstlens unit having a negative optical power and provided at the mostobject side of the zoom lens system, a second lens unit having anegative optical power, a third lens unit having a positive opticalpower, and a fourth lens unit having a positive optical power; andwherein said first lens unit through said fourth lens unit are disposedsequentially across a variable air gap.
 8. An optical device as claimedin claim 7 wherein the zoom lens system achieves zooming by varyingdistances between the first lens unit to the fourth lens unit.
 9. Anoptical device as claimed in claim 8 wherein the zoom lens systemfurther comprises a low-pass filter which adjusts spatial frequencycharacteristics of the optical image formed by the zoom lens system,said low-pass filter located between the first lens unit and the imagesensor.
 10. An optical device as claimed in claim 9 wherein the firstlens unit and the low-pass filter remain stationary during zooming. 11.An optical device comprising: a zoom lens system, comprising a pluralityof lens units, which achieves zooming by varying unit-to-unit distances;and an image sensor for converting an optical image formed by the zoomlens system into an electrical signal, wherein the zoom lens systemcomprises at least, from an object side thereof to an image sidethereof, a first lens unit having a negative optical power and beingprovided at the most object side of the zoom lens system, a second lensunit having a negative optical power, a third lens unit having apositive optical power, and a fourth lens unit having a positive opticalpower; and wherein the first lens unit is a single lens element.
 12. Anoptical device as claimed in claim 7 wherein the first lens unitcomprises two lens elements.
 13. An optical device as claimed in claim 7wherein the third lens unit comprises at least two positive lenselements and at least one negative lens element.
 14. An optical deviceas claimed in claim 7 wherein the third lens unit has an asphericalsurface at the image side thereof.
 15. An optical device comprising: azoom lens system, comprising a plurality of lens units, which achieveszooming by varying unit-to-unit distances; and an image sensor forconverting an optical image formed by the zoom lens system into anelectrical signal, wherein the zoom lens system comprises at least, froman object side thereof to an image side thereof, a first lens unithaving a negative optical power, a second lens unit having a negativeoptical power, a third lens unit having a positive optical power, and afourth lens unit having a positive optical power; wherein the third lensunit has an aspherical surface at the image side thereof; and whereinthe following conditional formulae is fulfilled:−0.6<(|X|−|X0|)/[C0·(N′−N)·f3]<0 0.1Ymax≦Y≦0.7Ymax wherein X representsa surface shape of the aspherical surface; X0 represents a surface shapeof a reference spherical surface of the aspherical surface; C0represents a curvature of the reference spherical surface of theaspherical surface; N represents a refractive index for a d-line of theobject-side medium of the aspherical surface; N′ represents therefractive index for the d-line of the image-side medium of theaspherical surface; f3 represents a focal length of the third lens unit;Ymax represents a maximum effective optical path of an asphericalsurface; and Y represents a height in a direction perpendicular to anoptical axis.
 16. An optical device as claimed in claim 7 wherein thefollowing conditional formula is fulfilled: 0.5<f1/f2<5 wherein f1represents a focal length of the first lens unit; and f2 represents afocal length of the second lens unit.
 17. An optical device comprising:a zoom lens system, comprising a plurality of lens units, which achieveszooming by varying unit-to-unit distances; and an image sensor forconverting an optical image formed by the zoom lens system into anelectrical signal, wherein the zoom lens system comprises at least, froman object side thereof to an image side thereof, a first lens unithaving a negative optical power, a second lens unit having a negativeoptical power, a third lens unit having a positive optical power, and afourth lens unit having a positive optical power; and wherein thefollowing conditional formulae are fulfilled: 1.5<|fl2/fw|<4 0.058<(tanωw)2×fw/TLw<0.9 wherein fl2 represents a composite focal length of thefirst and the second lens units at a wide-angle end; tan ωw represents ahalf view angle at a wide-angle end; fw represents a focal length of anentire optical system at the wide-angle end; and TLw represents adistance from a first vertex to an image plane at the wide-angle end.18. An optical device comprising: a zoom lens system, comprising aplurality of lens units, which achieves zooming by varying unit-to-unitdistances; and an image sensor for converting an optical image formed bythe zoom lens system into an electrical signal, wherein the zoom lenssystem comprises at least, from an object side thereof to an image sidethereof, a first lens unit having a negative optical power, a secondlens unit having a negative optical power, a third lens unit having apositive optical power, and a fourth lens unit having a positive opticalpower; and wherein the following conditional formulae is fulfilled:1.5<|fl2/fw|<4 10<TLw×Fnt/(fw×tan ωw)<50 where TLw represents a distancefrom a first vertex to an image plane at a wide angle end; Fntrepresents an f-number at a telephoto end; fl2 represents a compositefocal length of the first and the second lens units at the wide-angleend; fw represents a focal length of an entire optical system at thewide-angle end; and tan ωw represents a half view angle at thewide-angle end.
 19. An optical device as claimed in claim 7 wherein thelens unit closest to the image side has a positive optical power, saidlens unit is comprised of at least one positive lens element and thepositive lens element fulfills the following conditional formula:0.05<(CR1−CR2)/(CR1+CR2)<5 wherein CR1 represents a radius of curvatureof the object-side surface; and CR2 represents a radius of curvature ofthe image-side surface.
 20. An optical device comprising: a zoom lenssystem, comprising a plurality of lens units, which achieves zooming byvarying unit-to-unit distances; and an image sensor for converting anoptical image formed by the zoom lens system into an electrical signal,wherein the zoom lens system comprises at least, from an object sidethereof to an image side thereof, a first lens unit having a negativeoptical power, a second lens unit having a negative optical power, athird lens unit having a positive optical power, and a fourth lens unithaving a positive optical power; and wherein the following conditionalformula is fulfilled: 0.4<|fl2/f3|<1.5 where fl2 represents a compositefocal length of the first and the second lens units at a wide-angle end;and f3 represents a focal length of the third lens unit.